Bizarre RTF to MOBI conversion problem

[Gordon Bonnet]

I'm trying to use Calibre to convert RTF to MOBI, and it seems to be working (i.e. no error message), but then when I look at the MOBI file, it's deleted the entire document, EXCEPT words that were italicized. So I have a list of about five words or phrases per chapter (still in italics) -- and nothing else.

The same thing happens when I start with an EPUB version.

If I start with an HTM version, the text retains, but I lose formatting/page breaks.

Can anyone help? I'm working on a Mac, if that makes a difference, and I'm about to pull my hair out.

Thanks...